Synthetic Aperture Characterization of Radar Satellite Constellations

The concept of radar satellite constellations, or clusters, for SAR and other radar modes has been proposed and is currently under research. These systems are composed of multiple, formation-flying satellites with each satellite having its own, coherent receiver. Increased swathwidth compared to that of traditional SAR is attainable by processing the spatial data obtained from multiple satellites. The multi-channel system can also be scanned both forward and backward. The size and orientation of a such a system’s resolution cell can change dramatically, however, depending on the number of satellites in the constellation, the size of the constellation, the look geometry, and the subset of data that is coherently processed. In addition, any of these parameters can be varied on demand according to mission requirements. The constellation itself forms an array that is sparsely populated and irregularly spaced. Furthermore, if the constellation is of extremely wide extent, then the width of its array pattern determines resolution rather than system bandwidth and coherent integration length. The problem of predicting system resolution is further exacerbated by forwardand backwardlooking scenarios. In order to aid in the design, analysis, and signal processing of radar satellite constellations, we present a method of characterizing the resolution of such systems. We derive two eigensensors that can be interpreted as the dimensions of a twodimensional synthetic aperture. Then, the synthetic aperture expression is used to derive resolution; simulations are presented to verify the theory.